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There is no effect without a reason, and in allergology – there is no allergy without histamine. Persistent sneezing, runny discharge from the nose, itchy skin, and difficulty breathing, which may be hypersensitive, are largely due to the activity of this substance. When and how does histamine work in the body and why is it responsible for the development of allergic inflammation? We ask and answer in the article.
Histamine – role in the body
Every component of the body has a role to play in its functioning. This is also what happens with histamine. This chemical compound – referred to as a biogenic amine, produced mainly by mast cells (connective tissue and mucosa) and basophils (blood components from the leukocyte group) – mediates many important physiological processes.
How does histamine work? Responsible for regulating smooth muscle tone and glandular secretion. It mediates in the process of production and differentiation of blood morphotic elements (so-called hematopoiesis, i.e. hematopoiesis). It also participates in neurotransmission (transmitting information in the form of electrical impulses in the nervous system), promotes brain activity and supports our concentration.
In addition, histamine is involved in the process of fetal development, enables the transmission of intracellular signals in platelets and is responsible for wound healing. How much we need it to live is evidenced by the fact that histamine is found in every human organ and tissue.
It is stored in an inactive form on a daily basis (mainly in the lungs, mast cells and basophils). However, when the body is attacked by, for example, bacteria, a stressful situation occurs or physical exertion occurs, histamine is released, and after playing its role (accelerating the heart rate, increasing the efficiency of the heart, defending against aggressors causing inflammation or increasing the secretion of digestive juices) in the stomach) undergoing metabolism.
Histamine and an allergic reaction
Histamine is one of the main mediators of the inflammatory response. Its purpose is to defend the body against harmful chemical, physical or biological factors (microbes).
And how does histamine work in the body of an allergy sufferer? Well, the immune system of a person allergic to pollen, animal hair, food or house dust mites treats these factors as a serious threat to the system. As a result, contact with them is usually associated with the full mobilization of the immune system. Specific IgE antibodies are produced, marked by the presence of an apparent “enemy”, and histamine is massively released from the granules of some human immune cells.
Allergy (especially the early type) is associated primarily with the stimulation of the histamine H1 receptor. It is found in the respiratory system, central nervous system (CNS) and blood vessels. When stimulated by histamine, the allergy manifests itself as a result of the relaxation of the smooth muscles of small arteries, increased vascular permeability, as well as contraction of the smooth muscles of the bronchi and stimulation of the sensory nerve endings.
As for the H2 receptor, it is found in the gastric mucosa, CNS, heart and blood cells. The clinical consequence of its stimulation is an increase in the production of gastric juice, an increase in the secretion of sero-mucous glands in the respiratory tract and a reduction in the inflammatory reaction of the organism.
The H3 receptor is found in the gastric mucosa and the CNS. As a result of its stimulation, the synthesis of histamine and its release to the central nervous system takes place. The least known about the H4 receptor is found in the respiratory system, liver, spleen and marrow. Probably the role of this receptor is related to immunological processes – adds Zygmunt Nowacki, MD, PhD, allergist, specialist in children’s diseases, lecturer of the Polish Society for Combating Allergic Diseases.
How does histamine work?
Not every allergy sufferer is aware that histamine and allergy have a lot in common. However, everyone feels painfully the effects of the allergic reactions taking place in their body caused by the activity of this substance. – Shortness of breath, itching of the nose, sneezing, wheals or increased production of secretions in the bronchi – these are the most common symptoms associated with the increase in the concentration of histamine in our tissues – explains the doctor.
Histamine, by affecting the nasal mucosa and causing its inflammation, leads to the outflow of watery secretions and nasal blockage. By irritating the sensory nerve endings in these areas, it in turn causes itching and bouts of sneezing. In the course of skin allergies, histamine is responsible for itching and soreness, as well as local redness and warming of the skin.
It also causes local swelling as a result of the dilatation and increased capacity of the vessels. They concern both the skin (urticaria blisters located in its superficial layers or angioedema with the involvement of deeper parts of the skin) and the nose or throat.
In patients with asthma it may develop swelling of the larynx, trachea, bronchi and even lungs, which may cut off the air supply and cause difficulty breathing. In the case of eye allergies, histamine causes redness, tearing, itching and burning in the eyes, and swelling of the eyelids.
In turn, in patients with food allergy, it causes contraction of smooth muscles and increased production of digestive juices, and diarrhea due to irritation of the mucosa of the small intestine. On the other hand, when the concentration of histamine increases dramatically and it enters the bloodstream from the tissues, the patient is at risk of anaphylactic shock and, as a result, even death. The most common food allergens include casein, eggs, soy and cow’s milk. Find out if you should avoid these products by doing a 10-allergen mail-order test.
Histamine – second-generation antihistamines
Knowing the pathomechanism of allergic diseases and having a rational knowledge of the role of histamine in their course, pharmacologists have managed to create agents that antagonize this chemical compound.
Today, antihistamines are used in the first place and with great clinical effectiveness in patients suffering from seasonal and perennial rhinitis, allergic conjunctivitis or urticaria. Initially, antihistamines – the so-called first generation, e.g. antazoline, clemastine, promethazine – caused drowsiness, dementia and concentration disorders in patients, making it impossible, for example, to drive a car or impede learning.
All because they penetrated the blood-brain barrier, blocking also other receptors, including histamine receptors located in the central nervous system. Hence, there was a need to improve these preparations.
Currently, second-generation antihistamines provide greater safety of treatment, especially the newest ones, such as desloratadine or bilastine. Bilastine is a preparation completely dissimilar to the existing histaminics, it is fast (absorbed up to 1-1,5 hours) and effectively (works up to 26 hours) in suppressing symptoms caused only by the stimulation of the H1 receptor (urticaria, angioedema, itching, hay fever, ocular allergy symptoms).
The drug has an additional anti-inflammatory effect, and it is taken conveniently – orally, once a day. As the allergist assures: – Second-generation antihistamines are now widely used in medicine. We try to choose drugs with a high safety profile and selective action. Preparations blocking many histamine receptors are used very rarely. This sometimes occurs in hives and drug-induced allergic reactions.
Histamine is normally present in food, but it can also arise from maturation, or as a result of inadequate storage and spoilage of food. Among products with a high content of histamine we can mention, for example: blue cheeses, cured meats, silage, fish and seafood. People struggling with histamine intolerance should especially avoid these foods.
It is worth knowing that fresh, unprocessed products have little of this relationship. This is because the histamine content increases during food processing, and the longer food is stored or processed, the more its histamine content increases.
However, it should be remembered that the content of histamine in food products also depends on other factors such as in the case of fish, the conditions of their transport, the temperature in which they are kept and the species. Interestingly, it is histamine that causes the characteristic smell of rotten fish.
It should also not be forgotten that histamine does not decompose under the influence of increased temperature during frying or baking.
Histamine – effects
The ingestion of nutritious doses of up to 10 mg of histamine may cause a pseudoallergic reaction in susceptible individuals. In turn, in the case of a dose above 50 mg / kg of the product, we can already talk about the first symptoms of poisoning, i.e. hives, redness of the face, headache and burning of the mouth.
In the case of a dose above 200 mg of histamine per 1 kg of the product, the symptoms begin to worsen and include respiratory disorders and low blood pressure.
The dose of 1000 mg / kg of the product, in turn, leads to the so-called scombrotoxism, i.e. histamine poisoning, which manifests itself in respiratory disorders and may even end in death. It is worth knowing that the most common food poisoning caused by the content of histamine in food products concerns ripened cheese and fish such as mackerel, tuna, herring or sardines.
Symptoms of histamine intolerance
The symptoms of histamine intolerance are very similar to those that accompany an allergy. We’re talking rash of redness on the neck, chest, face, as well as headache and facial swelling here. In addition, it can also lead to nausea and diarrhea. Occasionally, symptoms such as arrhythmia or bronchial asthma appear.
Histamine intolerance or allergy?
To be sure whether in our case there is an allergy, or if we are dealing with histamine intolerance, we should perform a blood test, on the basis of which the activity of the DAO enzyme can be determined. This type of test can be performed in any laboratory and it is best to do it after observing your body after consuming certain foods.
It is also extremely important to consult a doctor who will assess whether we should supplement the DAO enzyme deficiency in our body, or whether it is enough to just use a low-histamine diet.
Find out more: Histamine intolerance. What is it manifested and how to treat it?
Histamine intolerance and diet
It’s good to know that each case of histamine intolerance must be considered individuallybecause it has to do with how your body reacts. Sometimes it is enough for some people to take dietary supplements and for others to completely exclude certain foods from the diet.
If there is a situation in which you do not want to eat foods containing histamine, remember that the presence of histamine in foods is strongly related to fermentation and maturation. For people who are strongly allergic to this chemical, you should limit the consumption of products containing histamine and focus on fresh and unprocessed foods. For example, choose fresh instead of smoked meat, and fresh fish instead of smoked or canned meat.
It is also worth adding products such as garlic, broccoli, leafy vegetables or onions to your diet. They contain quercitin, a compound that inhibits the secretion of histamine. It will also be a good idea to eat yoghurt, kefir or buttermilk due to the low histamine content. You should not forget about the supplementation of vitamin B6 and C, which are able to reduce the effects of histamine in our body.
Histamine Intolerance and Atopic Dermatitis
Atopic dermatitis (AD), which is an immunological, genetic and allergic disease characterized by itchy, dry and prone to irritation skin. Interestingly, we hear more and more voices about the association of AD with histamine intolerance.
This is due to the fact that AD symptoms can worsen as a result of many different factors, and one of them is stress related to the disease, for example, which causes an increase in the level of histamine and, consequently, may lead to symptoms related to its intolerance. In the case of atopic dermatitis, antihistamines are used to block the feeling of itching and as a complementary therapy.
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